Traditional motor vehicles typically have a single temperature-controlled zone air conditioning system designed to provide conditioned air to the front occupants in the passenger compartment of the vehicle. As the size of the vehicles increases, and as vehicle occupants demand more luxurious features, air conditioning systems capable of providing multiple temperature-controlled zones, or multi-zone air conditioning systems, have become more prevalent. A multi-zone air conditioning system allows the driver, front passenger, and even the rear seat passengers to have separate controls of the temperature and airflow in their respective zone, thereby maximizing the comfort of the occupants in each zone. A larger size vehicle, such as sport utility vehicles (SUV) and mini-vans, may have up to four or more individual zones in the passenger compartment. As an example, the passenger compartment of a mini-van may be divided into four separate zones, where the driver space may be zone 1, the front passenger space may be zone 2, the second row seating space may be zone 3, and the third row seating space may be zone 4.
Traditional heating, ventilation and air conditioning (HVAC) modules for single zone air conditioning systems are generally designed to optimally utilize the amount of available space in a given type of vehicle as well as to conform to the shape of that space. HVAC modules that have the capability of providing temperature control for multiple zones are specifically designed, tooled, and manufactured for the exact number of zones. The production volume for multiple zone HVAC modules is typically much lower than that for single or dual zone modules. As such, it is much more expensive to design such a multiple zone HVAC module for so few vehicles. Additionally, it would be disruptive to the manufacturing cell and the manufacturing process in general to be forced to build an entirely different HVAC module to achieve an additional temperature-controlled zone.
Traditional multiple zone HVAC modules use partition walls extending up to the individual heat exchangers within the HVAC module to provide multiple streams of conditioned airflow. These multiple streams of airflow are used to achieve multi-zone climate control in the associated passenger compartments. The greater the number of zones, the greater number of partition walls are required, and the larger the sizes of heat exchangers are required. However, multiple zone HVAC modules must conform to the limited size and shape of a where a single zone HVAC module would be in place, thereby requiring additional functions to be added without utilizing any extra space. Due to operating capacity and packaging constraints, two separate dual HVAC modules are occasionally employed in larger vehicles to achieve multi-zone operation, where a two zone module is installed in the area of the vehicle dash and another, one or two-zone, HVAC module in the area of the trunk.
However, implementation of the traditional, partitioned, dual HVAC modules, one under the dash and the other in the trunk, is cumbersome and costly. For example, dual HVAC modules can require excessive packaging space in the host vehicle, additional air ducts, additional lines and fittings, additional refrigerant, additional coolant, additional mass, higher operating noise levels, higher cost and increased system complexity that often translates into elevated quality and warranty issues. Such systems require additional energy and larger supporting components such as compressors, water pump, condenser, alternator, line sets, and ducts. As a consequence, the dual module approach results in increased vehicle fuel consumption and increased exhaust emissions. All of these items significantly contribute to overall vehicle cost and operating costs.
U.S. application Ser. No. 14/685,933 filed on Apr. 14, 2015, discloses a HVAC module capable of providing multiple temperature-controlled zones for a passenger vehicle, in which the HVAC module is sufficiently compact to reside within the dash of the vehicle. It is known to use a single airflow duct to convey conditioned air into each rear zone at the same discharge temperature. This is perfectly acceptable for the heating mode, where air is discharged to the floor outlets, and for the vent mode, where cool air is discharged to the chest level ventilation outlets. However, for bi-level mode of delivery, which requires the vent outlet to delivery slightly cooler air and the heater outlet to deliver slight warmer air, the prior art ducting system is unable to meet such a requirement and can only deliver air streams at the same temperature into the vent outlet and the heater outlet.